Actuation and control device for electric switchgear

ABSTRACT

A control and actuation device for opening and/or closing an electric switching device having at least one fixed contact and at least one movable contact, which includes an actuating device operatively connected to the movable contact and which supplies energy to perform opening/closure. The actuating device includes a motor with position control, which is operatively connected to the movable contact, and a power and control electronic unit which, following a tripping command, sends to the motor electrical signals for driving the motor so that the movable contact achieves a predefined rule of motion.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an actuation and control device foropening/closing electric switching means, for example circuit breakers,reclosers, disconnectors and the like particularly for high- andmedium-voltage transmission and/or distribution grids. The deviceaccording to the present invention is particularly adapted for use inhigh-voltage circuit breakers and is now described with reference tothis application without limiting in any way its scope of application.

An example of a single pole operated circuit breaker provided with aconventional actuation device is shown schematically in FIG. 1. A firstpost-shaped supporting isolator 2 is arranged on a supporting frame 1; asecond isolator 3 is arranged on the upper end of said first isolator,and an interruption chamber, with interruption mechanisms constituted byfixed contacts and movable contacts, is provided inside said secondisolator. Closure and opening are performed by respectively engaging anddisengaging the fixed contacts with respect to the movable contacts. Themovable contacts are operatively connected to an actuation rod, whichruns inside the isolator 1 from the movable contacts to the base of thepost. The rod is actuated by means of kinematic systems located in ahousing 4 at the base of the post and operatively connected to anactuating device 5. Actuating devices of high-voltage switches arecurrently of the mechanical or hydraulic type. The mechanical actuationdevice is generally provided with two springs, namely a closing springand an opening spring a stroke-limiting shock absorber, a reloadingmotor for the closing spring, and a mechanism for the followingoperations: converting the motion produced by the springs into atranslatory motion of the movable contact; reloading the opening spring:making the opening operation independent of the closing operation.

A schematic example of a device of this kind is shown in FIG. 2 in whichthe following elements can be recognized: an opening spring 10 anopening device 11 actuated by an electromagnet an eccentric element witha lever 12, a closing device 13 actuated by an electromagnet a mainshaft 14, an arm 15 which is rigidly coupled to the shaft 14, a closingspring 16, a shock absorber 17, a drum 18 and a gearmotor 19. There aremany configurations which are alternative to the one illustrated herebut in general the mechanical actuating devices of the prior art have avery large number of components which require long and complicatedpreliminary settings.

Although achieving the task for which they are meant, said devices havemany disadvantages in addition to the already mentioned mechanicalcomplexity. The movement of the movable contact is in fact determinedexclusively by the elastic characteristic of the opening and closingsprings; the rule of motion of the movable contact cannot be changed bythe user but is set during design. Actuating devices of the hydraulictype, in which the movement of the movable contact is ensured by adaptedhydraulic actuators can partially obviate these drawbacks but havedisadvantages linked to the presence of fluids particularly owing totheir temperature-sensitivity.

The absence of control over the rule of motion of the actuator alsorequires the presence of dampers or shock-absorbers to dissipate theresidual kinetic energy at the end of the actuating operation and toavoid uncontrolled impacts against the pole. Furthermore, precision inthe positioning of the movable contact is limited by a mechanism whichis inherently inaccurate owing to the presence of the springs.

Owing to the large number of components the devices of the prior artrequire maintenance in order to maintain their nominal behavior and thusensure repeatability of the actuation by compensating for variations dueto system wear and aging. Actuation repeatability in any case hasinherent limits.

SUMMARY OF THE INVENTION

Another problem is due to response times, i.e., to the elapsed timebetween the actuating command and the beginning of the movement of themovable contact which is currently on the order of a few milliseconds.

Another disadvantage is due to the high noise level of conventionaldevices which can require the use of acoustic insulation systems on thecasing of the switchgear in order to limit its environmental impact.

Moreover, the energy that must be supplied is higher than the energystrictly required to move the movable contact, since it is necessary toalso move the various mechanical elements of the switchgear.

The aim of the present invention is to provide an actuating and controldevice for electric switching means particularly of the high- andmedium-voltage type such as for example circuit breakers disconnectors,reclosers and the like which allows to move the movable contact of saidelectric switching means according to a predefined rule of motion.

Within the scope of this aim, an object of the present invention is toprovide a control and actuation device for electric switching meanswhich has reduced mechanical complexity.

Another object of the present invention is to provide a control andactuation device for electric switchgear which allows to predefine thepositioning precision of the movable contact both during opening andclosing operation.

Another object of the present invention is to provide a control andactuation device for electric switching means which ensuresrepeatability of the maneuver optionally compensating for variations dueto aging and wear.

Another object of the present invention is to provide a control andactuation device for electric switching means which has reduced responsetimes.

Another object of the present invention is to provide a control andactuation device for electric switching means which is highly reliable,relatively easy to manufacture and at competitive costs.

This aim these objects and others which will become apparent hereinafterare achieved by a control and actuation device for opening and/orclosing electric switching means such as circuit breakers, disconnectorsreclosers and the like having at least one fixed contact and at leastone movable contact said device comprising actuating means operativelyconnected to the movable contact, said actuating means supplying theenergy to perform opening/closing operation. The device according to theinvention is characterized in that said actuating means comprise aposition control motor which is operatively connected to the movablecontact and a power and control electronic unit which drives said motorso that the movable contact achieves a defined rule of motion.

Control of the rule of motion of the movable contact allows to ensureaccuracy and repeatability of the switching action. The actuating deviceis also considerably simplified with respect to switchgear of the priorart since it allows to eliminate the opening, and closing springs themotor for reloading the closing spring and all the mechanism that allowto perform the switching cycles: accordingly the size of the actuating,device is also reduced.

Further characteristics and advantages will become apparent from thedescription of some preferred but not exclusive embodiments of a controland actuating device for opening, and/or closing electric switchingmeans illustrated only by way of non-limitative example in theaccompanying drawings wherein:

FIG. 1 is a schematic view of a pole of a single pole operated circuitbreaker provided with a conventional actuation device;

FIG. 2 is a schematic view of an example of a conventional mechanicalactuation device;

FIG. 3 is a block diagram of a device according to the invention;

FIG. 4 is a view of a single pole operated high-voltage circuit breakerprovided with a device according to the invention;

FIG. 5 is a view of a possible embodiment of the kinematic linking in adevice according to the invention;

FIG. 6 is a view of another embodiment of the kinematic linking in adevice according to the invention;

FIG. 7 is a view of a particular embodiment of the device according tothe invention which can be applied to a single pole of a high-voltagecircuit breaker;

FIG. 8 is a view of a three-pole operated circuit breaker provided witha single actuating and control device according to the embodiment ofFIG. 5;

FIG. 9 is a view of a practical implementation of the device of FIG. 6;

FIG. 10 is a view of a three-pole operated circuit breaker provided witha single control and actuating device according to the embodiment ofFIG. 7;

FIG. 11 is a view of a single pole of a high-voltage circuit breakerprovided with a device according to another embodiment of the invention;

FIG. 12 is a view of a three-pole operated circuit breaker provided witha single control and actuating device according to the embodiment ofFIG. 11;

FIG. 13 is a view of an application of a particular embodiment of thedevice according to the invention to a three-pole operated circuitbreaker;

FIG. 14 is a sectional view taken along the plane 60—60 of FIG. 13.

With reference to FIG. 3 the control and actuating device according tothe invention comprises a control and power supply unit 100 whichfollowing a tripping command 106 (arriving for example from an operatoror from a protection system) drives the position control motor 101. Themotor 101 is operatively connected to the movable contact 103 of theelectric switching means of a suitable kinematic linking 102. The motor101 is driven by the unit 100 so that the movable contact 103 achieves apredetermined rule of motion.

Position control is generally performed by means of a position sensorlocated on the motor 101 which sends to the control unit 100 information107 related to the movement of said motor. Position control can also beperformed by a position sensor for the movable contact 103 which sendsto the control unit 100 information 108 related to the actual positionof the movable contact. Said position sensor can simply be a limitswitch which reports to the control unit 100 that the required switchingaction has been completed.

The control and power supply unit 100 can be powered directly by theelectric grid 104. However, the device preferably has an auxiliaryenergy-accumulation power supply system 105. Preferably said system,constituted for example by a battery of capacitors must be able to storeand deliver at least the energy required for a quickopening/closing/opening (OCO) switching cycle.

By means of the control and power supply unit 100 it is possible toprogram the rule of motion of the movable contact in a simple andflexible manner as a function both of the command and of the type offault possibly detected. It is also possible to predefine thepositioning precision of the movable contact, both during opening andduring closing, thereby reducing the risks of damage currently derivingfrom over-stroke problems. Position control performed on the motorand/or on the movable contact allows to brake the movable contact at theend of the switching action thus eliminating the need to use a shockabsorber.

Preferably the position control motor is constituted by a rotaryservomotor with a position sensor. In this case the connection betweenthe motor and the movable contact occurs by means of a kinematic linkingwhich is capable of converting the rotary motion of the driving shaftinto a substantially linear motion of the movable contact. The use of aservomotor allows high power levels to be available with very shortdelivery times. For an equal power it is furthermore possible to actwith two independent control parameters (torque and/or speed), allowinggreater flexibility during design.

Some non-limitative examples of possible embodiments of the kinematiclinking in a device according to the invention are shown schematicallyin FIGS. 5 and 6. With reference to FIG. 5 the motor 20 is operativelycoupled to the movable contact 27 by means of a kinematic linking whichcomprises a pinion 21 mounted on the output of the driving shaft. Thepinion 21 is coupled to a gear or, more simply as shown in FIG. 5 with agear sector 23. The sector 23 is rigidly coupled to a shaft 24 which isin turn rigidly coupled to a crank 25. The crank 25 is connected to amovable contact actuating rod 26 which transmits the motion to saidmovable contact 27. In the embodiment of FIG. 6 the motor 20 isoperatively coupled to the movable contact 27 by means of a kinematiclinking which includes a pinion 21 mounted on the output of the drivingshaft 22. The pinion 21 is coupled to a rack 30 which is rigidly coupledto an actuation rod 31 for the movable contact 27, thus converting therotary motion into a translatory motion of the movable contact. FIG. 9illustrates the practical implementation of the mechanism of FIG. 6; inparticular it shows at the base of one pole, the kinematic systemsdescribed in FIG. 6 and generally designated by the reference numeral200 the electronic system 201 and the energy storage system 202.

The device according, to the invention is conveniently applied invarious kinds of electric switching means, such as circuit breakers,disconnectors reclosers and the like and is particularly adapted forhigh-voltage circuit breakers. FIG. 4 illustrates an example of a singlepole operated high-voltage circuit breaker which comprises a control andactuating device according to the invention in the left part of thefigure the circuit breaker is shown in the closed position, while in theright part it is shown in the open position. In the case of the circuitbreaker shown in FIG. 4 the position control motor is a rotaryservomotor and connection between the motor and the movable contactoccurs by means of a mechanism of the type shown in FIG. 5.

Another example of possible application to a pole of a high-voltagecircuit breaker is shown in FIG. 7 in which the motor 20 is operativelycoupled to the movable contact not shown in figure by means of akinematic linking which comprises a pinion 21 which is mounted on theoutput of the driving shaft 2B. In particular the pinion 21 is coupledto a rack 30 in a manner similar to the one described in figure in thiscase according to a possible embodiment the rack 30 is in turn connectedto the actuating rod 26 of the movable contact by means of a systemconstituted by a crank 215 and a lever 32. Both the crank 25 and thelever 32 by virtue of the rotation of the motor and of the translatorymotion of the rack rotate rigidly with the shaft 24 and allow to convertthe rotary motion of the driving shaft into the translatory motion ofthe movable contact.

Another form of application to a single pole of a circuit breaker isshown schematically in FIG. 11 in which conversion of the motion fromrotary to translatory is achieved, according to another embodiment ofthe kinematic linking by using a worm screw which is integrated in themotor 20 and directly coupled to the actuating rod 26 in this case, therotation of the motor causes the consequent movement of the worm screwwhich in turn entails the consequent translatory motion of the rod 26.

If the electrical switching means is constituted by a three-polehigh-voltage circuit breaker for opening and closing a circuit connectedthereto, each individual pole can comprise an actuating and controlmechanism according to the invention. In this manner by appropriatelyprogramming the electronic control and power supply unit, it is possibleto provide a synchronous opening or closing action i.e. during aselected time-window in relation to the waveform of the electricalparameters. As an alternative as shown in FIGS. 810 and 12 thethree-pole circuit breaker can have a single actuating and controldevice according to the invention in one of the correspondingembodiments shown in FIG. 57 and 11 in such situations, the device ismechanically coupled to each individual pole of the switch by adoptingsuitable rods 33.

In particular. as shown in FIG. 12, if the kinematic linking entails theuse of a worm screw the worm screw 50 is integrated in the motor and asa consequence of the rotation of said motor forces the rod 33 to performa translatory motion the presence for each pole of a linking systemconstituted by a lever 25 and a crank 32 similar to what has alreadybeen described allows to obtain a corresponding translatory motion foreach one of the rods 26.

A further embodiment in the case of a three-pole operated circuitbreaker is shown in figures 13 and 14 in which the driving shaft 22 isdirectly connected to the rotation shaft 24 rigidly coupled to the crank25. In this manners the rotation of the shaft 22 entails the rotation ofthe shaft 24 and of the crank 25. Accordingly, this allows to havedirect actuation of the movable contact, (not shown in the figure),which is connected to the rod 26 and performs a translatory motion byvirtue of the rotation of the motor.

The actuating and control device according to the invention can befurthermore characterized by very short response times which are muchshorter than those of devices of the prior art which are on the order ofa few milliseconds. It has in fact been found that in the case ofhigh-voltage switches the response time can be less than 1 millisecondgenerally on the order of tens of microseconds. Response time is definedas the time elapsing between tripping command and beginning of themovement of the movable contact. High-voltage circuit breakerscharacterized by such short response times are not known in the state ofthe art. Accordingly, the present invention also relates to ahigh-voltage circuit breaker which is characterized in that the responsetime, defined as the elapsed time between tripping command and thebeginning of the movement of the movable contact is less than 1millisecond.

In practice it has been found that the actuating and control deviceaccording to the invention fully achieves the intended aim since itallows to improve the characteristics of electric switching means bycontrolling the rule of motion of the movable contact.

In addition to the above advantages, the actuating and control deviceallows to reduce costs by reducing the parts reducing the calibrationoperations and eliminating movements and stresses that can give rise toimpact damage. Accordingly maintenance costs are also reduced.

The device thus conceived is susceptible of modifications andvariations, all of which are within the scope of the inventive conceptall the details may furthermore be replaced with technically equivalentelements. In practice the materials used so long as they are compatiblewith the specific use as well as the dimensions may be any according tothe requirements and the state of the art.

What is claimed is:
 1. An actuation and control device for at least oneof opening and closing electric switching means having at least onefixed contact and at least one movable contact, comprising actuatingmeans which are operatively connected to the movable contact and supplythe energy to perform at least one of opening and closing, wherein, saidactuating means comprise a position control motor which is operativelyconnected to the movable contact, and a power and control electronicunit which drives said position control motor so that the movablecontact achieves a defined rule of motion, said position control motoris a rotary servomotor, and the connection between said position controlmotor and the movable contact is provided by means of a kinematic pairwhich is capable of converting a rotary motion of a driving shaft into atranslatory motion of the movable contact.
 2. An actuation and controldevice according to claim 1, comprising an auxiliary energy-accumulationsystem for supplying power to the electronic control and power supplyunit.
 3. An actuation and control device according to claim 2, whereinsaid auxiliary system is constituted by a battery of capacitors.
 4. Anactuation and control device according to claim 1, wherein positioncontrol is performed by a position sensor on the motor.
 5. An actuationand control device according to claim 1, comprising a movable contactposition sensor.
 6. A pole of a high-voltage circuit breaker, comprisingan actuation and control device for at least one of opening and closingelectric switching means having at least one fixed contact and at leastone movable contact, comprising actuating means which are operativelyconnected to the movable contact and supply the energy to perform atleast one of opening and closing, wherein, said actuating means comprisea position control motor which is operatively connected to the movablecontact, and a power and control electronic unit which drives said motorso that the movable contact achieves a defined rule of motion, saidposition control motor is a rotary servomotor, and the connectionbetween said position control motor and the movable contact is providedby means of a kinematic pair which is capable of converting a rotarymotion of a driving shaft into a translatory motion of the movablecontact.
 7. A three-pole high-voltage circuit breaker for opening andclosing a circuit connected thereto, wherein each individual polecomprises an actuation and control device for at least one of openingand closing electric switching means having at least one fixed contactand at least one movable contact, comprising actuating means which areoperatively connected to the movable contact and supply the energy toperform at least one of opening and closing, wherein, said actuatingmeans comprise a position control motor which is operatively connectedto the movable contact, and a power and control electronic unit whichdrives said motor so that the movable contact achieves a defined rule ofmotion, said position control motor is a rotary servomotor, and theconnection between said position control motor and the movable contactis provided by means of a kinematic pair which is capable of convertinga rotary motion of a driving shaft into a translatory motion of themovable contact.
 8. A three-pole circuit breaker according to claim 7,wherein the three-pole circuit breaker operates by synchronous openingor closing action.
 9. A three-pole high-voltage circuit breaker foropening and closing a circuit connected thereto, comprising: anactuation and control device for at least one of opening and closingelectric switching means having at least one fixed contact and at leastone movable contact, comprising actuating means which are operativelyconnected to the movable contact and supply the energy to perform atleast one of opening and closing, wherein, said actuating means comprisea position control motor which is operatively connected to the movablecontact, and a power and control electronic unit which drives said motorso that the movable contact achieves a defined rule of motion, and saidposition control motor is a rotary servomotor; and a mechanism forcoupling said actuation and control device to each individual pole ofthe switch, wherein the connection between said position control motorand the movable contact is provided by means of a kinematic pairconnected to the mechanism which is capable of converting a rotarymotion of a driving shaft into a translatory motion of the movablecontact.
 10. A high-voltage circuit breaker, comprising: at least onefixed contact and at least one movable contact; and actuation means forseparating the movable contact from the fixed contact upon a trippingcommand, wherein, said actuation means includes a rotary servomotor, anda connection between the rotary servomotor and the movable contact isprovided by means of a kinematic pair which is capable of converting arotary motion of a driving shaft into a translatory motion of themovable contact, and the response time, defined as the time elapsingbetween when the tripping command is sent and when the movable contactbegins to move, is less than 1 ms.